--Mysis relicta, a small shrimp-like Crustacean,
after Sars (enlarged).]

These facts all go to prove that the sea formerly covered the lowlands
of Sweden, Finland, and Northern Russia. The fauna of Scandinavia, as we
have seen, indicates that during the greater part of the Glacial period
the country was not directly connected with continental Europe as it is
now. It seems that the barrier of separation probably consisted of a
broad expanse of ocean on which floated numerous icebergs, which
originated from the Scandinavian glaciers as they reached the sea. This
was a cold sea, whilst Western Scandinavia was washed by the Gulf Stream
(_vide_ Fig. 12, p. 156). We might look upon the boulder-clay which
covers such vast tracts of country in Northern Germany, Russia, and
Holland as deposits formed by this sea rather than the ground-moraine of
a huge Scandinavian glacier. I shall refer to this subject again in the
next chapter; meanwhile it may be remembered that the boulder-clay of
Northern Europe exactly resembles in all important particulars the
similar accumulations met with in the British Islands. They resemble one
another also in the occasional occurrence of sea-shells, the frequent
appearance of bedded deposits, and the often inexplicable course taken
by boulders from their source of origin. There occurs often a singular
mixture and an apparent crossing of the paths of boulders in the
boulder-clay. Professor Bonney remarks (p. 280) that these are less
difficult to explain on the hypothesis of distribution by floating ice
than on that of transport by land-ice, because, in the former case,
though the drift of winds and currents would be generally in one
direction, both might be varied at particular seasons. So far as
concerns the distribution and thickness of the glacial deposits, he says
there is not much to choose between either hypothesis; but on that of
land-ice it is extremely difficult to explain the intercalation of
perfectly stratified sands and gravels and of boulder-clay, as well as
the not infrequent signs of bedding in the latter. Two divisions are
generally recognisable in the continental boulder-clay--a lower and an
upper. An inter-glacial phase characterised by a less severe climate is
assumed to have intervened between the deposition of the two. In Russia
no such division can as a rule be made out, and sea-shells are either
entirely absent or extremely scarce. It has been pointed out by
Professor J. Geiki